feat(editor): colour global variables (the semantic global modifier) (#1393)

lua-language-server marks globals with the `global` token modifier, but
the editor dropped it, so a global variable looked like a local unless
rainbow highlighting was on. The modifier now sets `cm-sem-global`, drawn
in a new Language Defaults › Identifiers › Global variable colour
(`--syn-global`): library globals keep the predefined colour and calls the
function-call colour. Imported IntelliJ themes and .icls schemes take it
from DEFAULT_GLOBAL_VARIABLE. Built-in schemes default it to the local
variable colour (IntelliJ's fallback for the key), so they look as before
until a scheme sets it.

Fixes #1370

src/features/plugins/intellijTheme.ts

@@ -130,6 +130,7 @@ export const ICLS_ATTRIBUTES: Record<string, Array<[Part, string]>> = {
   DEFAULT_IDENTIFIER: [["FOREGROUND", "--syn-variable"]],
   DEFAULT_LOCAL_VARIABLE: [["FOREGROUND", "--syn-variable"]],
   DEFAULT_PARAMETER: [["FOREGROUND", "--syn-param"]],
+  DEFAULT_GLOBAL_VARIABLE: [["FOREGROUND", "--syn-global"]],
   DEFAULT_PREDEFINED_SYMBOL: [["FOREGROUND", "--syn-builtin"]],
   DEFAULT_METADATA: [
     ["FOREGROUND", "--syn-annotation"],